patches/old/relayfs-introduce-getting-relayfs-statistics-function.patch

From: Jason Xing <kernelxing@tencent.com>
Subject: relayfs: introduce getting relayfs statistics function
Date: Thu, 12 Jun 2025 14:11:59 +0800

In this version, only support getting the counter for buffer full and
implement the framework of how it works.

Users can pass certain flag to fetch what field/statistics they expect to
know.  Each time it only returns one result.  So do not pass multiple
flags.

Link: https://lkml.kernel.org/r/20250612061201.34272-4-kerneljasonxing@gmail.com
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Yushan Zhou <katrinzhou@tencent.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/relay.h |    7 +++++++
 kernel/relay.c        |   30 ++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

--- a/include/linux/relay.h~relayfs-introduce-getting-relayfs-statistics-function
+++ a/include/linux/relay.h
@@ -31,6 +31,12 @@
 /*
  * Relay buffer statistics
  */
+enum {
+	RELAY_STATS_BUF_FULL = (1 << 0),
+
+	RELAY_STATS_LAST = RELAY_STATS_BUF_FULL,
+};
+
 struct rchan_buf_stats
 {
 	unsigned int full_count;	/* counter for buffer full */
@@ -167,6 +173,7 @@ struct rchan *relay_open(const char *bas
 			 void *private_data);
 extern void relay_close(struct rchan *chan);
 extern void relay_flush(struct rchan *chan);
+size_t relay_stats(struct rchan *chan, int flags);
 extern void relay_subbufs_consumed(struct rchan *chan,
 				   unsigned int cpu,
 				   size_t consumed);
--- a/kernel/relay.c~relayfs-introduce-getting-relayfs-statistics-function
+++ a/kernel/relay.c
@@ -701,6 +701,36 @@ void relay_flush(struct rchan *chan)
 EXPORT_SYMBOL_GPL(relay_flush);
 
 /**
+ *	relay_stats - get channel buffer statistics
+ *	@chan: the channel
+ *	@flags: select particular information to get
+ *
+ *	Returns the count of certain field that caller specifies.
+ */
+size_t relay_stats(struct rchan *chan, int flags)
+{
+	unsigned int i, count = 0;
+	struct rchan_buf *rbuf;
+
+	if (!chan || flags > RELAY_STATS_LAST)
+		return 0;
+
+	if (chan->is_global) {
+		rbuf = *per_cpu_ptr(chan->buf, 0);
+		if (flags & RELAY_STATS_BUF_FULL)
+			count = rbuf->stats.full_count;
+	} else {
+		for_each_online_cpu(i) {
+			rbuf = *per_cpu_ptr(chan->buf, i);
+			if (rbuf && flags & RELAY_STATS_BUF_FULL)
+				count += rbuf->stats.full_count;
+		}
+	}
+
+	return count;
+}
+
+/**
  *	relay_file_open - open file op for relay files
  *	@inode: the inode
  *	@filp: the file
_